Printed circuit edge connector

ABSTRACT

A printed circuit edge connector comprises contact springs having contact surfaces substantially parallel to the direction of insertion of a printed circuit board, each contact spring being loaded between three laterally spaced surfaces along a contact-receiving cavity of a housing so that the contact pressure is substantially constant over the whole area of the contact surfaces so that excessive wear against specific regions of the contact surfaces containing precious metal plating is thereby avoided.

2,983,896 5/1961 3,016,508 1/1962 Lalonde Luwcmrdmchfisfinll wrlings,'8- 3,l60,459 12/1964 Greco et al. M NM FOREIGN PATENTS [211 g fifi900,218 7/1962 Great Britain....... [45] Patented Aug. 24, 1971 PrimaryExaminer-Marvin A. Champion [73] Assignee Assistant Examiner-Robert A.Hafer Harrkburg, Pl. Altomeys-Curtis, Morris and Safford, Marshall M.

Holcombe, William Hintze, William J. Keating, Frederick Nahum W. Raring,John R. Hopkins, Adrian .1. La Rue and .la

Seitchik Vlijmen;

3 Claims, 3 Drawing Figs.

US. I

United States Patent [72] Inventors HermmuPetrnsJohannsGilken [22] Filed32 Priority Sept.30,l968

[541 PRINTEDCIRCUIT EDGECONNECTOR ABSTRACT: A printed circuit edgeconnector com tact springs having contact surfaces substantiallyparallel to the direction of insertion of a printed circuit board, eachcontact spring being loaded between three latera faces along acontact-receiving cavity of a hou contact pressure is substantiallyconstant over the whole area of the contact surfaces so that excessivewear regions of the contact surfaces containing ing is thereby avoided.

References Cited UNITED STATES PATENTS 5/1960 Fox 51 men @ATENTED M1824I971 SHEET 1 OF 2 1 link J .(mm 1/ g INVENTOR HERMANUS PETRUS JOHANNESmussEN LUCAS GERARDUS cHmsTmus TEURLINGS (12 M x ii PRINTED CIRCUIT EDGECONNECTOR This invention relates to electrical connectors and morespecifically to printed circuit edge connectors having preloaded contactSprings.

An electrical connector assembly for connecting an electrical lead to aprinted conductor on a printed circuit panel may comprise an insulatinghousing defining a channel for receiving an edge of the printed circuitpanel and a spring metal contact element disposed in the housing andhaving a contact spring portion having a contact surface or contactsurfaces for engaging the panel when inserted into the charmel, thecontact spring portion being formed as a loop which is stressed betweenabutment surfaces of the housing to preload the contact surface orcontact surfaces.

A disadvantage of known electrical connector assemblies of the kinddescribed above, is that the contact surface or contact surfaces areunevenly loaded so that the total contact force between the contactsurface or contact surfaces and the printed conductor are likewiseuneven. This leads to undue wear on the more heavily loaded areas of thecontact surface or contact surfaces, which are usuallygold-plated, as aresult of insertion and withdrawal of the printed circuit panel or ofvibration to which the assembly, when mated with the panel, may besubjected.

An object of the invention is to provide a printed circuit edgeconnector which is preloaded atthree spaced locations within acontact-receiving area of a dielectric housing.

Another object is the provision of a printed circuit edge connectorhaving contact surfaces extending substantially parallel to an insertionaxis thereof.

A further object is to provide a printed circuit edge connector havingaxially spaced contact surfaces along spring contact sections of contactelements.

An additional object is the provision of a printed circuit edgeconnector wherein the total contact force-to-contact surface deflectioncurve of the contact element rises sharply upon initial insertion of aprinted circuit board into the boardreceiving channel and thereafterremains substantially constant even where the board varies in thickness.

DESCRIPTION OF THE PREFERRED EMBODIMENT The attainments of the presentinvention will become apparent to those skilled in the art upon areading of the following detailed description when taken in conjunctionwith the drawings in which there is shown and described an illustrativeembodiment of the invention; it is to be understood, however, that thisembodiment is not intended to be exhaustive nor limiting of theinvention but is given forpurpose of illustration in order that othersskilled in the art may fully understand the invention and the principlesthereof and the manner of applying it in practical use so that they maymodify it in various forms, each as may be best suited to the conditionsof a particular use.

According to the invention, an electrical connector assembly forconnecting an electrical lead to a printed conductor on a printedcircuit panel comprises an insulating housing defining a channel forreceiving an edge of the printed circuit panel and a spring metalcontact element disposed in the housing and having a loop-shaped contactspring portion having a contact surface or contact surfaces for engagingthe panel when inserted into the channel, the contact surfaces extendingsubstantially parallel to the direction of insertion of the panel intothe channel and the contact spring portion being stressed between first,second and third abutment surfaces of the housing so that the contactsurfaceor contact surfaces of the contact portion are substantiallyconstantly loaded over the whole area of the contact surface or contactsurfaces.

For a better understanding of the invention, reference will now be madeby way of example to the accompanying drawings, in which:

FIG. 1 is a-cross-sectional view of an electrical connector assemblycomprising electrical contact elements disposed in a housing;

FIG. 2 is a side view of one of the contact elements prior to beingmounted in the housing; and

FIG. 3 is a view looking from the left of the contact element of FIG. 2.

The assembly shown in FIG. 1 comprises an elongate electricallyinsulating housing 1 defining a channel 2 for receiving in the directionof the arrow A in FIG. 1 the edge 3 of a printed circuit panel orboardhaving thereon printed conductors 4. The housing 1 defines pockets 5(only two of which are shown) each containing a spring metal contactelement 6.

Each element 6 comprises a contact spring portion formed as a loop, thebight 7 of which is directed upwardly (as seen in FIG. I) of the pocket5 in which the element 6 is disposed. Each element 6 is longitudinallydivided by a slot 8 (FIG. 3) between points a and b in FIG. 1 intotwo'parts of equal width to provide bifurcated contact spring portions.One arm 9 of each loop, which arm liesin the channel 2 and extendslongitudinally thereof has, as shown'in FIG. 3, four discrete contactsurface portions 10 to 13 defined by the slot 8 and by bights 14 bowedlaterally or inwardly of the insertion axis of channel 2. Each arm 9also has a free end portion 15 which is offset from the contact surfaceportions 12 and 13 of the arm 9. The other arm 16 of the loop has abight or bowed portion defining a projection 17 bowed towards thechannel 2 and from "which extends a portion 18 diverging from the arm 9downwardly (as seen in FIG. I) and having formed integrally therewith anelectrical-connecting post 19 having transverse lugs 20 in the vicinityof its junction with the portion 18.

The housing 1 has openings 21 each debouching into the base of one ofthe pockets 5 at one end and into the lower (as seen in FIG. 1 surfaceof the housing 1 at the other end. Each pocket 5 has a wall 22 extendingparallel to the channel 2 on one side thereof. A wall 23 extendingparallel to the wall 22 and centrally of the channel 2 has an upper (asseen in FIG. 1)

surface 24 forming a stop surface for the panel 3.

The posts 19 which are received in the openings 21 have portions 25extending from the lower (as seen in FIG. 1) wall of the housing 1 forconnection to electrical leads (not shown), e.g. by metallic clips or bywrapping the leads about the portions 25. In the present example, theposts 19 are of slightly oversized cross section with respect to theopenings 21. v

FIGS. 2 and 3 show one of the' contact elements 6 prior to insertion inits pocket 5. To insert each element 6 into the housing 1, the post 19of the element 6 is force-fitted into one of the openings 21 by engagingthe lugs 20 of the element 6 with a tool (not shown) to drive the post19 into the opening 21 until the lugs 20 of the element 6 engage ashoulder (not shown) in the opening 21 thus preventing further advanceof the post 19. As the post I9 is advanced into the opening 21, the loopof the element 6 is pressed laterally away from the channel 2 so thatthe portion 18 of the element 6 clears the adjacent wall 22 and theportion 15 of the contact element engages the wall '23 as the post 19 isbeing driven home, the crest of the bowed portion or projection 17engaging the side of the wall 22 remote from the channel 2. The element6 is thus under stress between the walls;22 and 23 and the laterallyouter side 21' of the wall of the jopening 21. The contact surfaceportions 10 and 11 are preloaded by the arm 16, the contact surfaceportions 12 and l3being preloaded by both the arms 9 and 16, eachcontact surface portion 10 to 13 being preloaded substantially to aconstant extent over the whole of its area. Thus when the panel 3 hasbeen inserted into the channel 2 to engage the surface 24, the contactforces exerted by the contact surface portions 10 to 13 against thepanel 3 are substantially equal. The radiused loops of elements 6 defineguide means to guide panel 3 between arms 9. The fact that the contactsurface portions 10 to 13 extend essentially parallel to the insertiondirection of the panel 3 and the fact that they are substantiallyequally preloaded reduces wear on conductive corrosion resistant coatingfor example gold, since i the contact pressure exerted by the contactsurface portions 10 to 13 against the panel 3 is substantially constantover the contact areas. The even engagement between the contact surfaceportions l to 13 and the panel 3 resulting from this even contactpressure ensures that even if the assembly is vibrated at its resonantfrequency there will be little damage to the plating, if present, on thecontact surface portions. Shifting of the panel 3 with respect to thehousing as a result, for example, of vibration causes little relativemovement between the contact surface portions to 13 and the panel 3 inview of the parallelism between these surface portions and the panel.

The preloading described above enables each arm 9 to be .spaced from thecenter of the channel 2 by a distance small enough to ensure that thedeflection of the contact surface portions 10 to 13 upon the insertionof the panel 3 into the channel 2 is small relative to the static.contact force exerted by the contact surface portions 10 to 13 againstthe panel 3 in its fully inserted position.

The total contact force-to-contact surface deflection curve of thecontact element rises sharply upon initial insertion of the panel 3 intothe channel 2 and thereafter remains substantially constant even wherethe panel varies in thickness.

The preloading of the contact surface portions as well as the shape ofthe curve, mentioned above, can be varied by altering the relativelengths and positioning of the arms 9 and 16 with respect to the post19.

The posts may be secured tothe housing by means other than force fittingas described above.

' Changes in construction will occur to those skilled in the art andvarious apparentlydifierent modifications and embodiments may be madewithout departing from the scope of the invention. The matter set forthin the foregoing description and accompanying drawings is offered by wayof illustration only. The actual scope of the invention is intended tobe defined in the following claims when viewed in their properperspective against the prior art.

The invention is claimed in accordance with the following:

1. An electrical connector comprising a dielectric housing having achannel and a pocket in communication'with said channel, said pockethaving an opening in communication therewith and a wall extendingsubstantially parallel to said channel, another wall at an inner end ofsaid channel and extending substantially parallel to said pocket wall, acontact element having a section disposed in said opening and a springcontact section including a portion extending along an inner surface ofsaid pocket wall, a loop spaced adjacent to and extending along an outerend of said pocket wall and contact surface means extending along saidchannel and being substantially parallel to an insertion axis of saidchannel, a free end of said spring contact section disposed inengagement with said another wall, and projection means provided by saidportion in engagement with said inner surface of said pocket wall, saidsection in said opening, said projection means in engagement with saidinner pocket wall surface and said free end in engagement with saidanother wall providing preloaded contact surface means substantiallyconstantly loaded over the whole area of said contact surface means.

2. An electrical connector assembly for connecting an electrical lead toa printed conductor on printed circuit panel, the

assembly comprising an insulating housing defining a channel forreceiving an edge of the printed circuit'panel'and a spring metalcontact element disposed in the housing and including a loop-shapedcontactv spring portion having contact surface means for engaging thepanel when inserted into the channel, the contact surface meansextending substantially parallel to the direction of insertion of thepanel into the channeland the contact spring portion being stressedbetween, first, second and third abutment surfaces of the housingso thatthe contact surface means of the contact portion is substantiallyconstantly loaded over the whole area of the Icontact surface means, thecontact spring portion having a free end part on one side of the loopformed by the contact spring'portio'n, this one side of the loopproviding the contact surface means the free end part of the loopengaging the first abutment surface,

the other side of the loop having a projection engaging the secondabutment surface which extends between the two sides of the loop andbeing stressed between the third abutment surface and the projection.

3. An electrical connector assembly for connecting an electrical lead toa printed conductor on a printed circuit panel, the assembly comprisingan insulating housing defining a channel having a'mouth for receiving anedge of a printed circuit panel to be inserted into the channel and aspring metal contact element disposed in the housing and having acontact spring portion formed in the shape of a loop one side of whichhas a flat contact surface or flat contact surfaces for engaging thepanel when inserted into the channel, such surface of surfaces extendingsubstantially parallel to the direction of insertion of the panel intothe channel, the loop-shaped contact spring portion being stressed byengagement of the contact element with first, second and third abutmentsurfaces of the housing, in such a way that the contact surface orcontact surfaces are substantially uniformly preloaded 'over the wholearea of the contact surface or contact surfaces, the first abutmentsurface being remote from the mouth of the channel and engaging a freeend portion of the one side of the loop-shaped contact spring portion,the second abutment surface engaging the other side of the loop-shapedcontact spring portion and cooperating with the third abutment surfaceto stress the other side of the loop-shaped contact spring portion, inwhich the first abutment surface is formed by a first wall of thehousing, disposed centrally of the channel and extending in theinsertion direction of the panel, the second abutment surface beingformed by a second wall of the housing, which wall is parallel to thefirst wall, the said'contact surface or contact surfaces extendingparallel to the second wall to the side of that wall facing the channel,the portion or portions of the said contact surface or surfaces nearestthe mouth of the channel being preloaded by that side of the loop-shapedcontact spring portion which is disposed on the opposite side of thesecond wall to the contact surface or surfaces, and the portion orportions of the contact surfaces nearest the base of the channel beingpreloaded by both sides of the loop-shaped contact spring portion, inwhich the first and second abutment surfaces are spaced from one anotherin the direction of insertion of the panel, the first abutment surfacelying between the second and third abutment surfaces in the direction ofinsertion of the panel, in which the other side of the loop-shapedcontact spring portion has a projection engaging the second abutmentsurface which lies between the two sides of the looped-shaped contactspring portion.

1. An electrical connector comprising a dielectric housing having achannel and a pocket in communication with said channel, said pockethaving an opening in communication therewith and a wall extendingsubstantially parallel to said channel, another wall at an inner end ofsaid channel and extending substantially parallel To said pocket wall, acontact element having a section disposed in said opening and a springcontact section including a portion extending along an inner surface ofsaid pocket wall, a loop spaced adjacent to and extending along an outerend of said pocket wall and contact surface means extending along saidchannel and being substantially parallel to an insertion axis of saidchannel, a free end of said spring contact section disposed inengagement with said another wall, and projection means provided by saidportion in engagement with said inner surface of said pocket wall, saidsection in said opening, said projection means in engagement with saidinner pocket wall surface and said free end in engagement with saidanother wall providing preloaded contact surface means substantiallyconstantly loaded over the whole area of said contact surface means. 2.An electrical connector assembly for connecting an electrical lead to aprinted conductor on printed circuit panel, the assembly comprising aninsulating housing defining a channel for receiving an edge of theprinted circuit panel and a spring metal contact element disposed in thehousing and including a loop-shaped contact spring portion havingcontact surface means for engaging the panel when inserted into thechannel, the contact surface means extending substantially parallel tothe direction of insertion of the panel into the channel and the contactspring portion being stressed between first, second and third abutmentsurfaces of the housing so that the contact surface means of the contactportion is substantially constantly loaded over the whole area of thecontact surface means, the contact spring portion having a free end parton one side of the loop formed by the contact spring portion, this oneside of the loop providing the contact surface means the free end partof the loop engaging the first abutment surface, the other side of theloop having a projection engaging the second abutment surface whichextends between the two sides of the loop and being stressed between thethird abutment surface and the projection.
 3. An electrical connectorassembly for connecting an electrical lead to a printed conductor on aprinted circuit panel, the assembly comprising an insulating housingdefining a channel having a mouth for receiving an edge of a printedcircuit panel to be inserted into the channel and a spring metal contactelement disposed in the housing and having a contact spring portionformed in the shape of a loop one side of which has a flat contactsurface or flat contact surfaces for engaging the panel when insertedinto the channel, such surface of surfaces extending substantiallyparallel to the direction of insertion of the panel into the channel,the loop-shaped contact spring portion being stressed by engagement ofthe contact element with first, second and third abutment surfaces ofthe housing, in such a way that the contact surface or contact surfacesare substantially uniformly preloaded over the whole area of the contactsurface or contact surfaces, the first abutment surface being remotefrom the mouth of the channel and engaging a free end portion of the oneside of the loop-shaped contact spring portion, the second abutmentsurface engaging the other side of the loop-shaped contact springportion and cooperating with the third abutment surface to stress theother side of the loop-shaped contact spring portion, in which the firstabutment surface is formed by a first wall of the housing, disposedcentrally of the channel and extending in the insertion direction of thepanel, the second abutment surface being formed by a second wall of thehousing, which wall is parallel to the first wall, the said contactsurface or contact surfaces extending parallel to the second wall to theside of that wall facing the channel, the portion or portions of thesaid contact surface or surfaces nearest the mouth of the channel beingpreloaded by that side of the loop-shaped contact spring portion Whichis disposed on the opposite side of the second wall to the contactsurface or surfaces, and the portion or portions of the contact surfacesnearest the base of the channel being preloaded by both sides of theloop-shaped contact spring portion, in which the first and secondabutment surfaces are spaced from one another in the direction ofinsertion of the panel, the first abutment surface lying between thesecond and third abutment surfaces in the direction of insertion of thepanel, in which the other side of the loop-shaped contact spring portionhas a projection engaging the second abutment surface which lies betweenthe two sides of the looped-shaped contact spring portion.